Actually, asthma is the body over reacting to foreign drugs, plants, mold, etc.  The immune system kicks into overdrive to attack and basically over reacts causing the symptoms of asthma.  I know this is true, as I have asthma myself.  When I control the allergies that I have my asthma is in much better control. 

I to have asthma and the medication is a blocker for allergens not a controller.  Again it deals with the immune system.  Our bodies will naturally block allergens but as our bodies no longer do that job we need medication to correct it.  Our bodies will continue to produce more antigens or antibodies until the allergen is blocked.  If our system is weakened then we cannot produce enough to correct the problem.

My asthma does not mean that my immune system is out of whack.  It means that my allergies cause my body, especially my lungs and sinuses, to over respond.  The inflammation in the airway is a direct result of my sensitivity to the allergens.  The inflammation becomes chronic and there is always some senstivity.  I, however, do not catch colds or viruses any easier than anyone alse.  I am able to fight off pretty much what anyone else can.  The medication in the inhaler does in fact control my asthma by reducing the chronic inflammation that is present and reducing the need for rescue inhalers.  The medication you use may do that but most aim for asthma control.

Another thing to remember is that allergens causes different reactions in different people...from nothing to life threatening.  Antibodies are not the same.  You develop antibodies to things like viruses and bacteria.  This becomes another complicated issue.